Apparatus for heat-treating fluent solids



May 14, 1957 F. D. DE VANEY ET Al- 2,792,132

APPARATUS FOR HEAT-TREATING FLUENT soLIDs 3 Sheets-Sheet l Filed July17, 1951 V -iim 'lllllllllllllllllllllllllllillll llllll INVENTOR Zw@Uma .BY/WW Wg/WM ATTORNELS May 14, 1957 F, D DE VANEY ETAL 2,792,132

APPARATUS FOR HEAT-TREATING FLUENT soLIDs Filed July 17, 1951 3Sheets-Sheet 2 /Vorma/ ATTORNEYS May 14, 1957 F. D. DE vANEY ETAL2,792,132

APPARATUS Foa HEAT-TREATING FLUENT soLIDs Filed July 17, 1951 5Sheets-Sheet 5 ATTORNEY United States Patent APPARATUS FOR HEAT-TREATINGFLUENT SOLIDS Fred D. De Varney, Hibbing, Minn., and Donald Beggs,

Toledo, hio, assignors to Erie Mining Company, Hibbing, Minn., acorporation of Minnesota Application July 17, 1951, Serial No. 237,209

7 Slaims. (Cl. 214-182) The present invention relates to apparatus forcontinuously laying down small masses, e. g., pellets, of mineralparticles, e. g., ore concentrates or fines, onto the stockline of agravitationally descending charge column within a shaft furnace, whereinthe small masses constituting the charge are subjected to a desired heattreatment. The invention is particularly concerned with the provision ofimprovements in the control of a loader mechanism for continuouslylaying down relatively fragile pellets of moist mineral particles in amanner to compensate for irregularities in the profile of the stockline,arising from irregularities in the rate of feed to the column and fromuneven descent of the column, and to maintain a substantially uniformstockline. The improved control mechanism is applicable generally tofurnace loaders which continuously travel over the stockline of thecharge either in a rotary manner in the case of a shaft furnace ofgenerally circular cross-section or in a reciprocatory manner in thecase of a shaft furnace of generally rectangular cross-section, and willbe described, in the following, with particular reference to rotaryloaders for pellet-indurating shaft furnaces. It is to be noted,however, that the improvements of the present invention are applicableto any type of shaft furnace, Whether used for pellet-indurating or forsome other heating or metallurgical operation, wherein it is desirableor necessary to maintain a uniform stockline without mechanicalrabbling.

In most shaft-type furnaces or chambers where a iluent material ischarged into the top and discharged from the bottom, the stoclrlineprofile obtained depends in most part either on the angle of repose ofthe material or the functioning of some mechanical leveling device suchas a rabbling arm. ln the art of indurating pellets of balledup moistparticles of mineral solids such as iron ore concentrates neither of theabove means can be used because (l) the irregularity of prolerepresented by an angle of repose amounts to too great a variation inthe length f travel of the countercurrent stream of heat-treating gas,and (2) mechanical rabbling would break up the relatively very feeble orfragile pellets or balls. Thus, in charging such pellets to theindurating furnace the same must be dropped-for only a minimumdistance-onto the stockline and thereafter not disturbed. The stocklineof the pellet-indurating furnace must be relatively uniform for tworeasons: Y

(l) The distance that the balls are dropped from the loader must bemaintained at a minimum in order to avoid breakage from excessiveimpact, and

(2) The velocity of gases leaving the stockline must be as uniform aspossible over the entire surface, which precludes hills and valleys ofany substantial magnitude. With hills and valleys the gas velocity wouldbe greater at the valley than at the peak of the hill. This uniformityof gas flow must be maintained in order to maintain `uniform drying andheat treating of the balls. The problem of maintaining the stocklineuniform in an indurating furnace in which the fluent material is 'ne elydropped onto the stockline and left undisturbed (i. e., not rabbled)deserves consideration and discussion.

2,792,132 Patented May 14, 1957 First assume that the stockline rate ofdescent is absolutely uniform over the entire surface: now, if theloader deposits 1% more feed continuously in a first area than in asecond area, the rst area will in time build up to a ridge with a valleyat the second area. In other words, no continuous error in feed can betolerated, even of small magnitude. Conversely, with an absoluteuniformity in feed distribution, no continuous differential in rate ofdescent of the stockline can be tolerated, in spite of which it is thefact that in the operation of such shafttype furnace, irregularities inthe rate of descent invariably occur. From a practical point of view,when dealing with commercial size shaft `furnaces, the following istrue:

(a) Any mechanical feeding mechanism will have some error in uniformityof distribution, where material is simply dropped onto the stockline,and

`(b) The stockline descent will always be subject to irregularities.

Thus, with no means for correction, the stockline cannot be maintaineddesirably uniform.

The expression substantially uniform stockline as used above is intendedto describe not only a charge column top surface which liessubstantially in a single horizontal plane but also a charge column topsurface which is intended to present, in cross-section, any 4otherpredetermined contour. Thus, said expression is specifically intended toapply to a dimpled stockline, i. e., to a charge column top surfacewhich, in cross-section, is characterized by two similar downwardlyconverging, merging, convexly arcuate lines. Such dimpled Ycontour is ormay be desired in situations where the countercurrent of heating gas isrin its entirety introduced'into the charge column about the peripheryof the latter and at a level a considerable distance below thestockline, and it is desirable or necessary that the flow of the heatinggas be as uniform as possible throughout the upperpart of the column. Insuch instances, the contour is dimpled so that the straight linedistances from a peripheral gas inlet point to all points on thestockline on the same side of the major vertical axis of the chargecolumn as the column.

The general object of the present invention is to pro-V il videautomatic means for maintaining a substantially uniform stockline byproviding correction in accordance with deviations from a normal inorder to maintain the deviations at a minimum.

According to the present invention, the novel means for maintaininguniformity of the -stockline comprises, in association ywith thetraveling loader mechanism of the sha-ft furnace, a control meansresponsive to a change in the prole of the stockline for varying therate of deposit of fluent material by the loader mechanism inversely asthe change in elevation of the profile to effect an increase in depositrate at valleys along said path and a decrease in ldeposit at hillsalong said path. In its preferred embodiment, the invention comprises,in association with the traveling loader mechanism, a loader carriagemechanism adjacent the top of the shaft furnace, a stockline feelerfunctioning `to gauge the stockline profile just ahead of the loadermechanism in its path of travel, and carriage drive control mechanism,responsive to said feeler, for varying the -rate of travel of the loadercarriage and hence for varying the thickness of the layer of fluentsolid masses laid down onto the stockline by the loader. The followingcomprise the basic elements ofthe apparatus involved:

(l) Shaft furnace into which material is charged at the top anddischarged from the bottom;

(2) Loader or feeder for distributing material onto the stockline;

(3) Conveyor for conveying material to the feeder;

(4) Carriage for carrying the loader over its feed path;

(5) Carriage drive for moving the carriage;

(6) Discharge mechanism for discharging material from the furnace;

(7) Discharge mechanism drive for actuating the discharge mechanism;

(8) Stockline feeler for gauging stockline elevation just ahead of theloader in its path of travel; and

(9) Carriage drive control responsive to position of stockline feeler tomaintain constant profile of stockline.

In its preferred form, the apparatus also includes a (10) Dischargecontrol responsive to position of stockline feeler to maintain averagestockline elevation.

In essence, the functioning of the improved apparatus organization is asfollows: the average elevation of the stockline of the charge column ismaintained within predetermined normal limits preferably by appropriateadjustment of the discharge rate, and lactual prole irregularities inthe stockline are reduced to a minimum by (a) feeling any low or higharea ahead of the loader mechanism, and (b) reducing or increasingrespectively the rate of travel of the loader carriage in passage of theloader over said area.

The invention will now be described 'with greater particularity withreference to the laccompanying drawing, in which Fig. l is a view invertical section of an indurating furnace of generally cylindricalconstruction having a rotatable carriage and loader supported therebyand in which is incorporated one embodiment of the invention;

Fig. 2 is a view of the furnace in part top plan illustrating theessential features of the loader carriage control;

Fig. 3 is a schematic electrical diagram appertaining to the automaticcontrol for the carriage drive motor and furnace discharge motor-according to the preferred em bodiment of the invention as illustratedin Figs. l and 2; and

Fig. 4 is also a schematic electrical diagram for a somewhat modifledembodiment of the invention.

With reference now to the drawings:

=In Fig. 1, a generally cylindrical and vertical, heatinsulated shaftfurnace is represented in cross-section at 1. For charging thiscylindrical type of furnace, a rotary type of loader or feeder isutilized. The principal components of this loader comprise a horizontalframe or carriage 2 made of structural iron having depending therefrom acircular trackway 3 supported by a plurality of rollers 4 journalled inbearing brackets 5 secured in spaced relation around the furnace on -ahorizontal offset portion of the furnace wall just below the furnacemouth. The center of trackway 3 is concentric with the vertical axis x-xof the furnace and hence carriage 2 is revolvable -about the furnaceaxis. Mounted upon the carriage at one side of the furnace axis x--x isa reciprocating type of conveyor consisting of 'an upper chute 6 andalower chute 7 connected to a diester type of reciprocating drivedesignated generally by reference numeral 8. This type of drive obtainsits power from an electric motor 9 by a belt and wheel 10 and the rotaryinput motion is converted into a reciprocating output motion of rod 11which is coupled by lever 12 and linkage 13 to the upper and lowerchutes 6 and 7 in such manner that the chutesrreciprocate simultaneouslyin opposite directions. Chutes 6 and 7 are arranged one above the otherin ya direction generally radial of the furnace axis x-x. With thediester type drive and the chute interlinked as shown, the radiallyoutward stroke of chute 6 and the simultaneous radially inward stroke ofchute 7 will be relatively rapid and the reverse strokes will be4relatively slow. Hence, as the chutes reciprocate, uent solid materialscarried to the furnace by an endless conveyor 'belt 14 and dropped ontothe inner end of chute 6 will be caused to travel radially outward tothe outer end thereof. The material is then transferred t-o the outerend of lower chute 7 and caused to travel radially inward and spill offthe side edges thereof onto the stockline 15 of a charge column 16 ofsimilar materials generally filling the furnace.

The upper chute 6 is substantially uniform in width throughout itslength yand serves to collocate the material. the lower chute 7 is,however, stepped downwardly in width in the radially inward `directionas seen in Fig. 2 in order to distribute the material uniformly over thestockline as -the carriage 2 rotates. For rotating carriage 2, thelatter is provided with a depending ring gear 17 meshed with the gear 18on the drive shaft of motor 19.

From a metallurgical point of View, furnace 1 correspends generally tothat disclosed in U. S. Patent No. 2,533,142, according to which latterthe shaft comprises an upper part A communicating with a lower part B,the two parts being so designed and positioned with respect to eachother as to provide a passageway therebetween and, as represented at 23and 24 respectively, lower and upper, annular, plenum spaces immediatelyadjacent and contiguous with free surfaces of the charge column at theupper end of lower part B and adjacent the lower end of upper part A,respectively. Offset from parts A and B is a chamber 25 providingcombustion space D, which communicates with parts A and B at plenumspaces 24 and 23 respectively. In the lower part B of the furnace thereis provided an inlet conduit 26 for a forced current of air supplied bypump 27 to be passed upwardly through the material in part B to plenumspace 23, thence into and through combustion space D, and finally toplenum space 24 and into and through the material in part A. At 28 isrepresented a fuel inlet for delivering iuid fuel to the combustionspace D for combustion in the air current whereby to thermally enrichthe latter prior to its passage through part A.

The pellets of fluent material undergo an indurating process as theydescend progressively through the furnace and are finally discharged atthe bottom of the furnace by means of a discharge mechanism which, inthe form illustrated, is comprised of an endless belt conveyor 30 drivenby an electric motor 31.

It has been explained that the principal objective sought by the presentinvention is the substantially complete elimination of all hills andvalleys in the profile of the stockline of the charge column in thefurnace. To this end, reference is now made in particular to Figs. 2 and3. A feeler cup 32, for sensing, i. e., determining the stocklineprofile is mounted at the outer end of an arm 33 whose inner end is madefast to a rocker shaft 34. Rocker shaft 34 is mounted for rotation in abracket 35 secured to'the carriage 2. Feeler cup 32 rides by gravityupon the surface of the stockline 15 and is located slightly in advanceof the leading side 7a of the tapered discharge chute 7 as viewed inFig. 2. That is, with rotation of the carriage 2 counterclockwise asindicated in Fig. 2 by the directional arrow, cup 32 occupies a positioncounterclockwise from the leading side 7a of chute 7 and is used todetermine the stockline profile slightly in advance of the rotation ofthe feeder chutes.

As the feeler cup 32 rides in a circular path over the stockline 15,part of which is shown in development in Fig. 3, it rises and fallsaccording to the hills 15a and valleys 15b in the stockline whichrepresent in a somewhat exaggerated manner the undesirable deviations inthe stockline profile from the uniformly even level indicated by theline 15e. The circuit of motor 19 which drives carriage 2 includes arheostat 36 connected in series therewith from the power line conductorsL1 and L2 and mounted within a housing 37 also carried by bracket 35.The position of the rheostat slider 38 on the resistor element 39 at anyinstant is governed by the essaies instant elevation of feeler cup 32,and the arrangement is such that the portion of resistor 39 in circuitwith carriage drive motor 19 increases from normal as feeler cup 32drops in a valley 15b in the stockline and decreases from normal vas thecup rises over a hill 15a in the stockline. To this end slider 38 can bemounted as shown upon an arm 40 secured to rock shaft 34 such that asarm 33 rises, arm 40 will be lowered, and vice versa. An increase inresistance from the normal setting is effective to slow down thecarriage motor drive from its normal rate of about one revolution perminute and hence the immediate result is to deposit the fluent materialat a greater than normal rate, per unit of travel, upon this valleyedportion of the stockline. In a similar manner, a decrease in resistancesignalled by a rise in cup 32 upon a hill is effective to speed up thecarriage drive motor 19 with the result that the fluent materialdeposited upon the hilled portion will be at a less-thannormal rate.Thus, by slowing down the rate of rotation of the carriage 2 and therebyalso the chutes 6 and 7 at any temporary valley in the stocklinedetected by feeler 32 and conversely increasing the rate of rotation atany temporary hill detected by feeler 32, the general result will be tomaintain the stockline at the same level throughout the entirerotational path of the feeder chutes. The control is progressive incharacter in that the change in speed of the carriage drive motor 19 isproportional to the rise or fall of the feeler cup 32 on the stockline15.

It will also be observed from Fig. 3 that a mercury type of switch 42 isalso included in the control circuit of the motor 31 which drives thedischarge conveyor 30 for switching in or out of the motor circuit acontrol resistor 43 connected in series between the power line, L1, L2and motor 31. With resistor 43 shunted out of the circuit of motor 31 byclosure of the contacts in switch 42, motor 31 will receive a higheroperating voltage, the effect of which is to cause it to run faster andhence increase the speed of the discharge conveyor belt 30 which in turneffects a corresponding increase in the rate at which the heat-treatedfluent material is discharged from the furnace.

Conversely, with resistor 43 connected in the circuit of motor 31 whichis the condition which obtains when the'contacts of switch 42 are open,the operating voltage for the motor is decreased, causing it, and hencealso the conveyor belt 30, to decrease in speed and hence effect adecrease in the discharge rate of the fluent material from the furnace.With the rheostat arm 3S at the normal position on resistance 39 aspictured in Fig. 3, the contacts of switch 42 can be closed or open.

Switch 42 is 'also conveniently located within housing 37 and can alsobe secured to arm 46 on the opposite side of the rock shaft pivot axis34a from feeler cup 32, As illustrated, the arrangement is such thatwhen the feeler cup 32 rides the stockline at the normal level 15Csought to be maintained, or is above such level, switch 42 will betipped to such an angle that the mercury 42a therein bridges and closesthe circuit at the switch contacts 42b thus shunting out resistor 43 andcausing discharge conveyor 30 to operate at its fast rate and withdrawuent material from the furnace at a greater rate than it is beingbrought to the furnace by conveyor 14. The effect of this will be toslightly lower the general level of the stockline 15. Then when thegeneral level of the stockline has decreased to a point below the normalaverage, switch 42 is tipped upward to a posi tion wherein the mercury42a will no longer bridge and close the circuit across the switchcontacts 42b. Control resistor 43 is thereby reconnected in the circuitof motor 31 and the latter will run at its slow rate to thereby effectwithdrawal of the material from the furnace at a lesser rate than it isbeing brought to the furnace by conveyor 14. The effect of this will beto raise the average level of the stockline 15 back to at least normal,

6 whereupon the control cycle will be repeated. Thus Yby the huntingtype of control wherein the discharge rate of the material from thefurnace is cyclically increased and decreased, a generally averageelevation of the stockline will be maintained in the furnace. A somewhatsimilar type of'control for maintaining the average elevation of thestockline is disclosed and claimed in application Serial No. 6,743,tiled February 6, 1948, in the name'of Carl W. Sisco, now Patent No.2,646,900.

From the foregoing description it should now be clearly apparent thatthe two motor controls shown in Fig. 3 operate in conjunction with eachother, the control for motor 31 serving to maintain an average elevationof -the stockline 15 and the control for motor 19 serving to remove anyhills and valleys from the profile of the stockline regardless of itsinstant average height.

A modified type 4of control over the speed of the carriage drive motoris illustrated in Fig. 4 wherein means are provided for running motor 19at three speeds, high, normal and low, as distinguished from therheostat control of Fig. 3 wherein the speed of motor 19 is varied moredirectly proportionally to the size of the hills and valleys in thestockline prole.

With reference now to Fig. 4, wherein elements which are the same as inFig. 3 have been assigned the same reference numbers, it v/ill be seenthat the circuit from motor 19 Ito the line conductors L1, L2 includestwo resistors 44, 45 connected in series therewith, and that controlover these resistors which are arranged to be selectively shunted out ofthe motor circuit is exercised by two mercury switches 46, 47 mounted onarm 41, the resistors 44, 45 and their shunting switches 46, 47 takingthe place of the rheostat 36 in the Fig. 2 control. Also mounted on arm41 is another mercury switch 42 which functions to control the speed ofthe material discharge device in the same manner as in the Fig. 3arrangement. Mercury switches 46 and 47 are so adjusted on theirsupports that the contacts of both will be open whenever the feeler cup32 'detects a low spot or valley 15b in the stockline profile. Underthese conditions both resistors 44, 45 remain in series circuit relationwith the carriage drive motor 19 causing the carriage and materialloader to rotate at the low speed. When feeler cup 32 rides thestockline at the normal profile as depicted in Fig. 4, switch 46 willremain lopen but switch 47 will be elo-sed, thus shunting out resistor44 through conductors 4d, 49 and 50 and causing the carriage drive motor19 to operate at its middle or normal speed. When feeler cup 32 detectsa hill 15a in the profile of the stockline as measured along itscircular path around the stockline, mercury switch 46 will also closewhich is effective to shunt out both resistors 44, 4S through conductors4S, 51 and 52, whereupon carriage drive motor 19 is caused to run at itshigh speed.

Control over the speed of the material discharge as explained above iseffected through mercury switch 42 which operates in the same manner asin the Fig. 3 circuit and preferably the mercury switches 42 and 47 areso adjusted that their contacts close at the s-ame time.

Thus, as long as carriage 2 travels at the normal speed the feeder chute7 will deposit on the stockline 15 a material layer of norm-al (anduniform) thickness, whereas the chute 7 will deposit a thinner thannormal layer when the carriage is traveling at the high speed, and athicker than normal layer when the carriage is traveling at the lowspeed. Hence, as long as stockline feeler 32 feels a stockline surfacewhose levelness is within the limits of normal range, the carriage 2travels at normal rate causing feeder chute 7 to lay down a pellet layerof normal, uniform thickness. When, however, feeler 32 encounters astockline surface portion whose height is greater than normal (i. e.,hits a high spot in the profile of the stockline), the rate of angularmovement of the carriage 2 is increased to high" speed and feeder chute7 is caused 'to deposit a thinner than normal 'ferred to in the specificdisclosure.

'conveyor in its longitudinal travel.

layer of pellets. As soon as feeler 32 passes over the high spot andencounters a stockline surface portion whose height is within the normalrange, the rate of movement of carriage 2 is decreased to normal speed,whereupon feed chute 7 is caused to deposit a pellet layer of normalthickness. When feeler 32 encounters a stockline surface portion whoseheight is less than normal (i. e., hits a low spot in the stocklineprofile), the rate of movement of carriage 2 is decreased from normalspeed to low speed and feeder chute 7 is caused to deposit a thickerthan normal layer of pellets on stockline for so long as feeler 32continues to signal the presence of the low spot, thus tending tocorrect the low spot, whereafter the rate of movement of carriage 2 isadvanced to normal speed and feeder chute 7 of the loader is caused todeposit a pellet layer of normal thickness.

By thus controlling and varying the speed of travel of the loadercarriage 2, the relative thickness of the pellet layer laid down on thestockline 15 is m-ade self-compensating to the end that hills andvalleys will be eliminated from the stockline prole practically as fastas they start to appear.

Conventional slip rings and brushes are utilized for connecting switch42 and rheostat 36 according to the Fig. 3 arrangement or the switches42, 46 and 47 according to the Fig. 4 arrangement into their respectivecontrol circuits for thev loader carriage drive motor 19 and thematerial discharge drive motor 31; the brushes 53 are carried by androtate with the carriage 2, and the slip rings 54 on which the brushesride are arranged one above the other and are secured about theperiphery of the furnace 1.

It is to be noted that the principle of stockline profile controlinherent in the two specific embodiments above described in Figs. 3 and4 can be applied equally as well to a rectangular furnace as to thecylindrical furnace re For example, the simplest way to feed arectangular furnace is to use a belt conveyor carried by a reciprocatingcarriage so that the point of discharge of the belt conveyor is causedto travel generally longitudinally back and forth over the stockline.The average stockline elevation is maintained normal by regulating therelative furnace discharge rate to feed rate, in a manner similar tothat above disclosed. The actual deviations from normal in stocklineprofile can be maintained at a minimum by regulating the speed of travelof the ltraveling carriage whereby the belt conveyor feeder, driven at aconstant speed, deposits more or less material in low or high spots. Thestockline feeler is arranged to determine the stockline elevation justahead or in the vicinity of the point of feed of the belt In certainpossible paths of feed travel over the stockline, two feelers may berequired due to direction reversal of the traveling carriage.

It is to be noted that levelling out of the hills and valleys in thestockline is effected by varying the speed of travel of the travelingcarriage without regard to the rate at which the pellets are deliveredto the point of discharge from the carriage by the feeder conveyor 14,This condition cannot be otherwise for the pellets must be carried alongby conveyor 14 from their source, namely the balling drum, at whateverrate they are discharged from the drum. The reason for this stems forthe fragile nature of the pellets as they leave the drum which makes itimpossible to deliver them to some intermediate storage point from thedrum and from wherever they could be carried as needed to the furnace bythe feeder 14. Consequently, it would not be practical to effectlevelling of the stockline by keeping the speed of the carriage constantand adjusting the rate of delivery of the pellets to the carriage fromthe feed conveyor 14.

Moreover, in certain applications of the invention where no control overthe discharge rate may be required it is obvious that this component ofthe organization, namely the variable drive for the discharge device 30,30 can be omitted.

In conclusion we desire it to be understood that the various embodimentsof our invention as described and illustrated are to be considered astypical rather than exhaustive of the structural variation possiblewithin bounds of our invention and that in accordance therewith, variousother arrangements may be developed without, however, departing from thespirit and scope of our invention as defined in the appended claims.

We claim:

l. In a shaft furnace whereinto fluent solid material is fed at the topand wherefrom heat-treated fluent solid fmaterial is discharged from alower part thereof, and

wherein an average stockline elevation is maintained, the combination ofa loader for distributing a layer 0f fluent solid material in a pathover the stockline, a carriage for transporting the loader over saidpath, a variable speed drive mechanism for propelling the carriage alongsaid path at variable speed, a determining device for determining theprofile of the stockline along said path of said loader, saidprofile-determining device including a mechanical feeler device ridingin surface contact with said stockline in the path of said loader andsensing deviations in stockline height above and below such averagestockline elevation, and means controlled by said feeler device forautomatically varying the speed of said drive mechanism whereby to movethe loader at a higher than normal rate of speed when the same isfeeding to an area of the stockline which is above average height and tomove the loader at a lower than normal rate of speed when the same isfeeding to an area of the stockline which is below the average height.

2. The invention as defined in claim l wherein said variable speed drivemechanism includes an electric motor and a speed changing elementconnected in circuit therewith and controlled by said stockline profiledetermining device.

3. The invention as defined in claim 2 wherein said speed changingelement is constituted by a rheostat the slider arm of which iscontrolled by said stockline profile determining device.

` 4. The invention as defined in claim l wherein said variable speeddrive mechanism includes an electric motor and speed changing elementsselectively connectable in circuit therewith by said stockline profiledetermining device to effect stepped changes in the motor speed.

5. The invention as defined in claim 4 and wherein said speed changingelements are selectively connected in circuit with said motor byswitches controlled by said stockline profile determining device.

6. The invention as defined in claim 1 wherein the fiuent solid materialis withdrawn from said furnace by an electrical discharge deviceoperable at different speedsI and the speed of operation thereof iscontrolled by switch' means actuated by said stockline profiledetermining device.

7. The invention as defined in claim l wherein said stockline profiledetermining means is constituted by a mechanical feeler device riding insurface contact with said stockline at one end of a crank arm, the otherend of said arm being secured to a rock shaft, and the drive means forsaid carriage is constituted by an electric motor having a speed controltherefor actuated by said rock shaft in accordance with the angulardisplacement thereof.

References Cited in the file of this patent UNITED STATES PATENTS Y1,666,027 Beaumont Apr. l0, 1928 1,961,893 Wadman et al lune 5, 19342,030,448 Hardgrove Feb'. 11, 1936 2,219,954 Geiger et al. Oct. 29, 19402,277,879 Ness et al. Mar. 31, 1942 2,636,606 Dunasky et al. Apr. 28,1953

